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MERLIN LEGEND Communications System Release 6.1
Network Reference
555-661-150
Issue 1
August 1998
Call-Handling Scenarios
Page 2-18Network Configuration Scenarios
2
Tandem PRI trunks provide the following benefits:
■ Faster General Performance. PRI facilities make faster connections
across private networks for ARS calling over tandem trunks as well as
faster intersystem call handling.
■ Faster Data Transmission. Networked PRI tandem trunks support digital
data speeds of up to 128 kbps between networked systems for enhanced
2B data videoconferencing and other data applications. Earlier releases
permitted a maximum speed of 112 kbps between connected systems.
NOTE:
If you plan to communicate at 64 or 128 (2B data) kbps, use
extended superframe (ESF) format with Bipolar 8-Zero Substitution
(B8ZS) line coding. Some service providers charge more for this
type of T1 circuit. However, it not only allows the higher speed, it is
also less susceptible to line errors than other format and coding
combinations and can be maintained without taking the facility out of
service.
■ Better Call-Handling Displays. Intersystem calls via networked PRI
facilities can provide the caller’s extension label (for example, caller name),
extension number (factory setting), or both name and number at the
recipient’s MLX telephone display. Scenario 1 shows the details for
different types of telephones.
■ Lower Service Provider Costs. When you use PRI over a private
network, you order a point-to-point T1.5 circuit from your service provider,
then program the PRI service yourself rather than leasing it from the
service provider. When networked systems are distant, the service provider
may need to provide amplification but not PRI switching services.
■ Fractional Use Support. You may place drop-and-insert equipment
between systems connected by a PRI tandem trunk, allowing use of fewer
than 23 B-channels. The dropped channels are generally used for
dedicated data/video service, and the remaining channels carry voice
traffic. The equipment must never drop Channel 24, the D-channel. All
channels do count towards the system maximum of 80 lines.
■ Automatic Number Identification (ANI)/Incoming Call Line
Identification (ICLID). If PRI tandem trunks are used, ANI and ICLID
information may display at the destination extension.
■ Better Transfer Handling. When a user manually transfers a call across
the private network on tandem PRI trunks and the transfer recipient’s
extension is either busy or has turned on Do Not Disturb and has no
coverage available, the call returns to the transfer originator. If a call is
transferred over tandem tie trunks, or is transferred with automatic
completion over tandem PRI trunks, it does not return to the originator
when the intended destination is unavailable.